Molecular mechanisms mediating the G protein-coupled receptor regulation of cell cycle progression

G protein-coupled receptors are key regulators of cellular communication, mediating the efficient coordination of a cell's responses to extracellular stimuli. When stimulated these receptors modulate the activity of a wide range of intracellular signalling pathways that facilitate the ordered development, growth and reproduction of the organism. There is now a growing body of evidence examining the mechanisms by which G protein-coupled receptors are able to regulate the expression, activity, localization and stability of cell cycle regulatory proteins that either promote or inhibit the initiation of DNA synthesis. In this review, we will detail the intracellular pathways that mediate the G protein-coupled receptor regulation of cellular proliferation, specifically the progression from the G1 phase to the S phase of the cell cycle

GZ coupling to the rat κ-opioid receptor

AbstractWe have expressed the cloned rat κ-opioid receptor in human embryonic kidney 293 cells and studied the ability of κ-selective ligands to inhibit adenylyl cyclase. In transfected 293 cells, activation of the κ-opioid receptor by U50,488 and the dynorphins resulted in the inhibition of cAMP accumulation. The inhibitory response was sensitive to pertussis toxin and highly selective for κ-agonists; neither μ- nor θ-opioids were able to activate the κ-opioid receptor. Upon co-transfection with the α subunit of Gz, inhibition of cAMP accumulation by κ-agonist became refractory to pertussis toxin, indicating that the κ-opioid receptor can couple to both Gi and Gz proteins

G z Can Mediate the Acute Actions of -and -Opioids but Is Not Involved in Opioid-Induced Adenylyl Cyclase Supersensitization 1

ABSTRACT The three subtypes of opioid receptors (␦, , and ) are known to regulate multiple effectors through either pertussis toxinsensitive or -insensitive G proteins. In opioid-induced inhibition of adenylyl cyclase, both G i and G z proteins can serve as the signal transducer. Our previous study showed that opioid-induced adenylyl cyclase supersensitization in human embryonic kidney (HEK) 293 cells expressing the ␦-opioid receptor requires G i but not G z proteins. Herein, we studied the ability ofand -opioid receptors to regulate the activities of adenylyl cyclase through G z . In HEK 293 cells coexpressing G z with the -or -opioid receptors, opioid agonists induced inhibition of adenylyl cyclase in a pertussis toxin-insensitive manner. However, adenylyl cyclase supersensitization induced by chronic opioid treatments remained sensitive to pertussis toxin. We also showed that the responsiveness of cAMP-dependent response element-binding proteins to forskolin was not altered after prolonged opioid treatment but was higher in cells coexpressing G z . Although the -and -opioid receptors mediated acute activation of extracellular signal-regulated protein kinase 1/2 via both G i and G z , these responses were abolished by chronic opioid treatment. These studies showed that G z could mediate acute actions of -and -opioids but G z alone was insufficient to mediate adenylyl cyclase supersensitization induced by the chronic activation of opioid receptors. Opioids induce their biological effects by binding to three subtypes of opioid receptors (␦, , and ). The opioid receptors are distributed throughout the central and peripheral nervous systems Adenylyl cyclase (AC) is the typical effector of opioid receptors. Acute stimulation of opioid receptors leads to inhibition of AC activity. A compensatory increase in AC activity is often induced after chronic opioid treatment. This phenomenon is observed in a variety of cell types, including the simian kidney fibroblast COS-7, Chinese hamster ovary, and neuroblastoma ϫ glioma hybrid NG 108-15 cell

Segment and track neurons in 3D by repulsive snake method

We present a snake (active contour) model based on repulsive force to segment neurons obtained from microscopy. Based on these segmentation results, we track the neurons in 3D image to look for its branch structure. These segmentation results allow user to study morphology of neurons to further investigate neuronal function and connectivity. This repulsive snake model can successfully segment two or multiple neurons that are close to each other by some alternating repulsive force generated from the neighboring objects. We apply our results on real data to demonstrate the performance of our method. © 2005 IEEE.published_or_final_versio

Paediatric Epilepsy Surgery Programme in Hong Kong: experience in Queen Mary Hospital / Duchess of Kent Children's Hospital

Poster: no. P6BACKGROUND: Surgery is a well-established treatment for adults with intractable seizures. Increasingly, infants and children are being considered for epilepsy surgery. In a growing child, epilepsy surgery has the additional benefit of aborting cognitive decline and improving development and behaviour ...published_or_final_versio

Paediatric Epilepsy Surgery Programme in Hong Kong: experience in Queen Mary Hospital/Duchess of Kent Children's Hospital

Poster: no. P6BACKGROUND: Surgery is a well-established treatment for adults with intractable seizures. Increasingly, infants and children are being considered for epilepsy surgery. In a growing child, epilepsy surgery has the additional benefit of aborting cognitive decline and improving development and behaviour. METHODS: The paediatric epilepsy surgery programme ...published_or_final_versio

Chimeric Gαq mutants harboring the last five carboxy-terminal residues of Gαi2 or Gαo are resistant to pertussis toxin-catalyzed ADP-ribosylation

AbstractThree widely-used Gαq chimeras harboring the last five residues of Gαi, Gαo and Gαz (qi5, qo5 and qz5) were examined for their ability to serve as substrates for pertussis toxin (PTX)-catalyzed ADP-ribosylation. In COS-7 cells coexpressing one of the three opioid receptors (μ, δ, and κ) and a Gαq chimera, agonist-induced stimulation of phosphoinositide-specific phospholipase C (PI-PLC) was largely insensitive to PTX treatment. Only the qi5-mediated stimulation of PI-PLC by κ-opioids was partially inhibited by PTX. In βγ-release assays, PTX treatment did not affect the ability of opioid receptors to activate these chimeras. [32P]ADP-ribosylation labeled Gαi/o but not qi5 or qo5, although the expression of these chimeras was confirmed by immunodetection. Thus, Gαq chimeras with a Gαi/o-like tail are insensitive to PTX treatment

Clinical and molecular epidemiological features of coronavirus HKU1-associated community-acquired pneumonia

Background. Recently, we described the discovery of a novel group 2 coronavirus, coronavirus HKU1 (CoV-HKU1), from a patient with pneumonia. However, the clinical and molecular epidemiological features of CoV-HKU1-associated pneumonia are unknown. Methods. Prospectively collected (during a 12-month period) nasopharyngeal aspirates (NPAs) from patients with community-acquired pneumonia from 4 hospitals were subjected to reverse-transcription polymerase chain reaction, for detection of CoV-HKU1. The epidemiological, clinical, and laboratory characteristics of patients with CoV-HKU1-associated pneumonia were analyzed. The pol, spike (S), and nucleocapsid (N) genes were also sequenced. Results. NPAs from 10 (2.4%) of 418 patients with community-acquired pneumonia were found to be positive for CoV-HKU1. All 10 cases occurred in spring and winter. Nine of these patients were adults, and 4 had underlying diseases of the respiratory tract. In the 6 patients from whom serum samples were available, all had a 4-fold change in immunoglobulin (Ig) G titer and/or presence of IgM against CoV-HKU1. The 2 patients who died had significantly lower hemoglobin levels, monocyte counts, albumin levels, and oxygen saturation levels on admission and had more-extensive involvement visible on chest radiographs. Sequence analysis of the pol, S, and N genes revealed 2 genotypes of CoV-HKU1. Conclusions. CoV-HKU1 accounts for 2.4% of community-acquired pneumonia, with 2 genotypes in the study population. Without performance of diagnostic tests, the illness was clinically indistinguishable from other community-acquired pneumonia illnesses. © 2005 by the Infectious Diseases Society of America. All rights reserved.published_or_final_versio